1. Field of the Invention
The present invention relates to an electro-hydraulic power steering apparatus having a hydraulic pump driven by a motor.
2. Background Art
The conventional electric power steering apparatus decelerates a rotational output of an electric motor to become an auxiliary steering torque and transmits it to an output shaft of a hand steering gear, assisting a manual steering effort applied to a steering wheel to turn the wheels. In the conventional electric power steering apparatus motor, a disc spring for applying a pre-load to the rotational shaft along the shaft center in a direction toward the bearing is held between an outer ring portion of bearing and a yoke bearing housing. Also, in the conventional electric power steering apparatus, the motor has a motor housing composed of a receiving portion of concave shape for receiving the bearing at the opposite end of the output side and a yoke, with a vibration absorbing material interposed between the bearing received in the receiving portion and the receiving portion (e.g., refer to JP-A-11-252851, paragraphs [0002] to [0004], [0014], FIG. 7A, FIG. 1). Moreover, some of the conventional electric pumps had a noise damper barrel communicating to a discharge chamber or an elastic body in a drive joint (e.g., refer to JP-A-10-82377 paragraphs [0014], [0018], FIG. 1, FIG. 8).
In the conventional electro-hydraulic power steering apparatus, although the bearing for rotatably bearing the rotational shaft was supported via the elastic body, the bearing was not pressed in the axial direction by the elastic body. Accordingly, there was a problem that a great noise was produced from the electro-hydraulic power steering apparatus, especially under the influence of pulsating hydraulic pressures of the hydraulic pump driven by the rotational shaft.